Remarks and experiments on the construction of respiratory waveforms from electrocardiographic tracings

We report on some observations and preliminary experiments on the deduction of respiratory waveforms from electrocardiographic traces by interpolating the values of angles related to a cardiac electrical axis. The experiments concern comparing the trends obtained from different definitions of the cardiac electrical axis: respiratory waveforms deducted by considering the electrical axis of either the QRS complex or the T wave, and those deducted in the presence of cardiac rhythm disorders, noise, and drifts. The most significant result was obtained when, starting from an ECG trace, we were able to plot curves that were very close to the respiration curve obtained from a belt impedance meter. This result indicates that the objective can be attained. Other results concern specific cases and the constraints to be observed. Among those, arrhythmia, missing beats, pauses, noise, and drifts superimposed on the original ECG traces.